Oxidation process to produce a crude and/or purified carboxylic acid product

ABSTRACT

Disclosed is an oxidation process to produce a crude carboxylic acid product carboxylic acid product. The process comprises oxidizing a feed stream comprising at least one oxidizable compound to generate a crude carboxylic acid slurry comprising furan-2,5-dicarboxylic acid (FDCA) and compositions thereof. Also disclosed is a process to produce a dry purified carboxylic acid product by utilizing various purification methods on the crude carboxylic acid.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 61/489,488 filed May 24, 2011, the disclosures of which are herein incorporated by reference in their entirety to the extent they do not contradict the statements herein.

FIELD OF THE INVENTION

The present invention relates to a process to produce a carboxylic acid composition. The process comprises oxidizing at least one oxidizable compound in an oxidizable raw material stream in the presence of an oxidizing gas stream, solvent stream, and at least one catalyst system.

More particularly, the present invention relates to a process to produce a carboxylic acid composition comprising furan-2,5-dicarboxylic acid (FDCA) and compositions thereof. The process comprises oxidizing 5-hydroxylmethyl)furfural in the presence of oxygen, a saturated organic acid solvent having from 2-6 carbon atoms, and a catalyst system at a temperature of about 100° C. to about 220° C. to produce the carboxylic acid composition comprising furan-2,5-dicarboxylic acid.

BACKGROUND OF THE INVENTION

Aromatic dicarboxylic acids, such as terephthalic acid and isophthalic acid, are used to produce a variety of polyester products. Important examples of which are poly (ethylene terephthalate) and its copolymers. These aromatic dicarboxylic acids are synthesized by the catalytic oxidation of the corresponding dialkyl aromatic compounds which are obtained from fossil fuels, which is disclosed in U.S. Patent Application 2006/0205977 A1), which is herein incorporated by reference to the extent it does not contradict the statements herein.

There is a growing interest in the use of renewable resources as feed stocks for the chemical industry mainly due to the progressive reduction of fossil reserves and their related environmental impacts. Furan-2,5-dicarboxylic acid (FDCA) is a versatile intermediate considered as a promising closest biobased alternative to terephthalic acid and isophthalic acid. Like aromatic diacids, FDCA can be condensed with diols such as ethylene glycol to make polyester resins similar to polyethylene terephthalate (PET) (Gandini, A.; Silvestre, A. J; Neto, C. P.; Sousa, A. F.; Gomes, M. J. Poly. Sci. A 2009, 47, 295.). Therefore, there is a need in the chemical industry for an efficient process to produce carboxylic acid compositions, especially FDCA. A high yield process (minimum of 90% FDCA yield) to produce a dry, purified FDCA product is provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates different embodiments of the invention wherein a process to produce a dried purified carboxylic acid 710 is provided.

FIG. 2 illustrates an embodiment of the invention, showing the GC chromatogram of the carboxylic acid composition 110 that has been dried.

FIG. 3 illustrates an embodiment of the invention, showing a ¹H NMR of the carboxylic acid composition 110 that has been dried.

FIG. 4 illustrates an embodiment of the invention, showing a ¹³C{¹H} NMR of the carboxylic acid composition 110 that has been dried.

FIG. 5 illustrates an embodiment of the invention, showing the effects of temperature, pressure, cobalt and bromine concentrations have on the FDCA yield in the carboxylic acid composition 110.

FIG. 6 illustrates an embodiment of the invention, Effect of temperature on yield using an oxidizable raw material stream 30 comprising 5-AMF. The + symbol represents that Co is 2000 ppm and Br is 3000 ppm. The x symbol represents that Co is 2500 ppm and Br is 2500 ppm.

FIG. 7 illustrates an embodiment of the invention, Effect of temperature on yield using an oxidizable raw material stream 30 comprising 5-EMF. The + symbol represents that Co is 2000 ppm and Br is 3000 ppm. The x symbol represents that Co is 2500 ppm and Br is 2500 ppm.

DETAILED DESCRIPTION

It should be understood that the following is not intended to be an exclusive list of defined terms. Other definitions may be provided in the foregoing description, such as, for example, when accompanying the use of a defined term in context.

As used herein, the terms “a,” “an,” and “the” mean one or more.

As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination, B and C in combination; or A, B, and C in combination.

As used herein, the terms “comprising,” “comprises,” and “comprise” are open-ended transition terms used to transition from a subject recited before the term to one or more elements recited after the term, where the element or elements listed after the transition term are not necessarily the only elements that make up the subject.

As used herein, the terms “having,” “has,” and “have” have the same open-ended meaning as “comprising,” “comprises,” and “comprise” provided above.

As used herein, the terms “including,” “includes,” and “include” have the same open-ended meaning as “comprising,” “comprises,” and “comprise” provided above.

The present description uses numerical ranges to quantify certain parameters relating to the invention. It should be understood that when numerical ranges are provided, such ranges are to be construed as providing literal support for claim limitations that only recite the lower value of the range as well as claim limitations that only recite the upper value of the range. For example, a disclosed numerical range of 10 to 100 provides literal support for a claim reciting “greater than 10” (with no upper bounds) and a claim reciting “less than 100” (with no lower bounds).

The present description uses specific numerical values to quantify certain parameters relating to the invention, where the specific numerical values are not expressly part of a numerical range. It should be understood that each specific numerical value provided herein is to be construed as providing literal support for a broad, intermediate, and narrow range. The broad range associated with each specific numerical value is the numerical value plus and minus 60 percent of the numerical value, rounded to two significant digits. The intermediate range associated with each specific numerical value is the numerical value plus and minus 30 percent of the numerical value, rounded to two significant digits. The narrow range associated with each specific numerical value is the numerical value plus and minus 15 percent of the numerical value, rounded to two significant digits. For example, if the specification describes a specific temperature of 62° F., such a description provides literal support for a broad numerical range of 25° F. to 99° F. (62° F.+/−37° F.), an intermediate numerical range of 43° F. to 81° F. (62° F.+/−19° F.), and a narrow numerical range of 53° F. to 71° F. (62° F.+/−9° F.). These broad, intermediate, and narrow numerical ranges should be applied not only to the specific values, but should also be applied to differences between these specific values. Thus, if the specification describes a first pressure of 110 psia and a second pressure of 48 psia (a difference of 62 psi), the broad, intermediate, and narrow ranges for the pressure difference between these two streams would be 25 to 99 psi, 43 to 81 psi, and 53 to 71 psi, respectively

In one embodiment of the invention, a process is provided to produce carboxylic acid composition and/or dry purified carboxylic acid 710 comprising furan-2,5-dicarboxylic acid (FDCA). Embodiments of the process are represented in FIG. 1. The process comprises oxidizing at least one oxidizable compound in an oxidizable raw material stream 30 in the presence of an oxidizing gas stream 10, solvent stream 20, and at least one catalyst system. The oxidizable raw material stream 30 comprises at least one oxidizable compound suitable to produce a carboxylic acid composition 110 comprising FDCA. The amount of FDCA in the carboxylic acid composition 110 can range from greater than 10 by weight percent in the carboxylic acid composition 110, greater than 20 by weight percent in the carboxylic acid composition 110, greater than 30 by weight percent in the carboxylic acid composition 110. The carboxylic acid composition 110 comprises FDCA and solvent.

In another embodiment of the invention, the process comprises oxidizing at least one oxidizable compound in an oxidizable raw material stream 30 in the presence of an oxidizing gas stream 10, solvent stream 20, and at least one catalyst system. The oxidizable raw material stream 30 comprises at least one oxidizable compound selected from the group consisting of 5-(hydroxymethyl)furfural (5-HMF), 5-HMF esters (5-R(CO)OCH₂-furfural where R=alkyl, cycloalkyl and aryl), 5-HMF ethers (5-R′OCH₂-furfural, where R′=alkyl, cycloalkyl and aryl), 5-alkyl furfurals (5-R″-furfural, where R″=alkyl, cycloalkyl and aryl), mixed feedstocks of 5-HMF and 5-HMF esters, mixed feedstocks of 5-HMF and 5-HMF ethers, mixed feedstocks of 5-HMF and 5-alkyl furfurals to generate a carboxylic acid composition comprising FDCA. The process can optionally include removing impurities from the carboxylic acid composition 110 in a liquid displacement zone 225 to form a low impurity slurry stream 210. The low impurity slurry stream 210 can be further treated in a secondary oxidation zone 335 to produce a secondary oxidation slurry stream 310 which can be routed to a crystallization zone 425 to form a crystallized slurry stream 410. The crystallized slurry stream 410 is cooled in a cooling zone 430 and the cooled crystallized slurry stream 510 can be routed to a solid-liquid separation zone 625 to generate a purified wet cake stream 610 comprising FDCA that is dried in a drying zone 725 to generate a dried, purified carboxylic acid 710 comprising purified FDCA.

In one embodiment of the invention, a process is provided to produce a dried, purified carboxylic acid 710 comprising dried, purified furan-2,5-dicarboxylic acid (FDCA) and comprises the following steps:

-   Step (a) comprises oxidizing at least one oxidizable compound in an     oxidizable raw material stream 30 in the presence of an oxidizing     gas stream 10, solvent stream 20, and at least one catalyst system     in a primary oxidation zone 125 which comprises at least one primary     oxidizer reactor to produce a carboxylic acid composition 110     comprising furan-2,5-dicarboxylic(FDCA); wherein the oxidizable raw     material stream 30 comprises at least one oxidizable compound     selected from the group consisting of 5-(hydroxymethyl)furfural     (5-HMF), 5-HMF esters (5-R(CO)OCH₂-furfural where R=alkyl,     cycloalkyl and aryl), 5-HMF ethers (5-R′OCH₂-furfural, where     R′=alkyl, cycloalkyl and aryl), 5-alkyl furfurals (5-R″-furfural,     where R″=alkyl, cycloalkyl and aryl), mixed feedstocks of 5-HMF and     5-HMF esters, mixed feedstocks of 5-HMF and 5-HMF ethers, and mixed     feedstocks of 5-HMF and 5-alkyl furfurals. Structures for the     various oxidizable raw material compounds are outlined below:

The 5-HMF or its derivatives are oxidized with elemental O₂ in a multi-step reactions, eqs 1 and 2, to form FDCA with 5-formyl furan-2-carboxyic acid (FFCA) as a key intermediate.

In one embodiment of this invention, streams routed to the primary oxidation zone 125 comprises an oxidizing gas stream 10 comprising oxygen and a solvent stream 20 comprising solvent, an oxidizable raw material stream 30, and a catalyst system. Oxidizable raw material stream 30 comprises a continuous liquid phase. In another embodiment of the invention, the oxidizable raw material stream 30, the oxidizing gas stream 10, the solvent stream 20 and the catalyst system can be fed to the primary oxidization zone 125 as separate and individual streams or combined in any combination prior to entering the primary oxidation zone 125 wherein said feed streams may enter at a single location or in multiple locations in the primary oxidization zone 125.

The carboxylic acid composition 110 comprises FDCA and FFCA. In another embodiment the FFCA in the carboxylic acid composition 110 ranges from about 0.1 wt % (weight percent) to about 4 wt % or 0.1 wt % to about 0.5 wt %, or 0.1 wt % to about 1 wt %. In another embodiment of the invention the carboxylic acid composition 110 comprises FDCA and FFCA and at least one of 2,5-diformylfuran in an amount ranging from 0 wt % to about 0.2 wt %, levulinic acid in an amount ranging from 0 wt % to 0.5 wt %, succinic acid in an amount ranging from 0 wt % to 0.5 wt % and acetoxy acetic acid in an amount ranging from 0 wt % to 0.5 wt %. In another embodiment of the invention the carboxylic acid composition 110 comprises FDCA, FFCA and EFCA. In other embodiment of the invention the EFCA in the carboxylic acid composition 110 in an range from about 0.05 wt % to 4 wt %, or about 1 wt % to 2 wt %.

The catalyst system comprises at least one catalyst suitable for oxidation. Any catalyst known in the art capable of oxidizing the oxidizable compound can be utilized. Example of suitable catalysts comprise at least one selected from, but are not limited to, cobalt, bromine and manganese compounds, which are soluble in the selected oxidation solvent. In another embodiment of the invention, the catalyst system comprises cobalt, manganese and bromine wherein the weight ratio of cobalt to manganese in the reaction mixture is from about 10 to about 400 and the weight ratio of cobalt to bromine is from about 0.7 to about 3.5.

The oxidizing gas stream comprises oxygen. Examples include, but are not limited to, air and purified oxygen. The amount of oxygen in the primary oxidation zone ranges from about 5 mole % to 45 mole %, 5 mole % to 60 mole % 5 mole % to 80 mole %.

Suitable solvents include water and the aliphatic solvents. In an embodiment of the invention, the solvents are aliphatic carboxylic acids which include, but are not limited to, aqueous solutions of C₂ to C₆ monocarboxylic acids, e.g., acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, trimethylacetic acid, caprioic acid, and mixtures thereof. In another embodiment of the invention, the solvent is volatile under the oxidation reaction conditions to allow it to be taken as an off-gas from the oxidation reactor. In yet another embodiment of the invention the solvent selected is also one in which the catalyst composition is soluble under the reaction conditions.

The most common solvent used for the oxidation is an aqueous acetic acid solution, typically having a concentration of 80 to 99 wt. %. In especially preferred embodiments, the solvent comprises a mixture of water and acetic acid which has a water content of 0% to about 15% by weight. Additionally, a portion of the solvent feed to the primary oxidation reactor may be obtained from a recycle stream obtained by displacing about 80 to 90% of the mother liquor taken from the crude reaction mixture stream discharged from the primary oxidation reactor with fresh, wet acetic acid containing about 0 to 15% water.

Suitable solvents include, but are not limited to, aliphatic mono-carboxylic acids, preferably containing 2 to 6 carbon atoms and mixtures thereof and mixtures of these compounds with water. Examples of aliphatic mono-carboxylic acids, include, but are not limited to acetic acid.

Generally, the oxidation temperature can vary from about 100° C. to about 220° C. and from about 110° C. to about 160° C.

In another embodiment of the invention, a process is provided to produce furan-2,5-dicarboxylic acid (FDCA) in high yields by liquid phase oxidation that minimizes solvent and starting material loss through carbon burn. The process comprises oxidizing at least one oxidizable compound in an oxidizable raw material stream 30 in the presence of an oxidizing gas stream 10, solvent stream 20, and at least one catalyst system in a primary oxidation zone 125; wherein the oxidizable compound is at least one selected from the group consisting of H(C═O)—R—(C═O)H, HOH2C—R—(C═O)H, and 5-(hydroxymethyl)furfural (5-HMF). The oxidizable compound can be oxidized in a solvent comprising acetic acid with or without the presence of water with oxygen in the presence of a catalyst system comprising cobalt, manganese and bromine, wherein the weight ratio of cobalt to manganese in the reaction mixture is from about 10 to about 400 and the weight ratio of cobalt to bromine is from about 0.7 to about 3.5. Such a catalyst system with improved Co:Mn ratio can lead to high yield of FDCA. In this process, the oxidation temperature can vary from about 100° C. to about 220° C., or another range from about 110° C. to about 160° C., which can minimize carbon burn. The cobalt concentration of the catalyst can range from about 1000 ppm to about 6000 ppm, and the amount of manganese from about 2 ppm to about 600 ppm, and the amount of bromine from about 300 ppm to about 4500 ppm with respect to the total weight of the liquid in the reaction medium of the primary oxidation zone 125. As used herein, process temperature is the temperature of the reaction mixture within the primary oxidation zone where liquid is present as the continuous phase. The primary oxidizer reactor will typically be characterized by a lower section where gas bubbles are dispersed in a continuous liquid phase. Solids can also be present in the lower section. In the upper section of the primary oxidizer, gas is in the continuous phase and entrained liquid drops can also be present.

In various embodiments of the invention, the catalyst compositions employed in the processes of the invention comprise cobalt atoms, manganese atoms, and bromine atoms, supplied by any suitable means, as further described below. The catalyst composition is typically soluble in the solvent under reaction conditions, or it is soluble in the reactants fed to the oxidation zone. Preferably, the catalyst composition is soluble in the solvent at 40° C. and 1 atm, and is soluble in the solvent under the reaction conditions.

The cobalt atoms may be provided in ionic form as inorganic cobalt salts, such as cobalt bromide, cobalt nitrate, or cobalt chloride, or organic cobalt compounds such as cobalt salts of aliphatic or aromatic acids having 2-22 carbon atoms, including cobalt acetate, cobalt octanoate, cobalt benzoate, cobalt acetylacetonate, and cobalt naphthalate.

The oxidation state of cobalt when added as a compound to the reaction mixture is not limited, and includes both the +2 and +3 oxidation states.

The manganese atoms may be provided as one or more inorganic manganese salts, such as manganese borates, manganese halides, manganese nitrates, or organometallic manganese compounds such as the manganese salts of lower aliphatic carboxylic acids, including manganese acetate, and manganese salts of beta-diketonates, including manganese acetylacetonate.

The bromine component may be added as elemental bromine, in combined form, or as an anion. Suitable sources of bromine include hydrobromic acid, sodium bromide, ammonium bromide, potassium bromide, and tetrabromoethane. Hydrobromic acid, or sodium bromide may be preferred bromine sources.

In another embodiment of the invention, a process is provided for producing furan-2,5-dicarboxylic acid (FDCA) in high yields by liquid phase oxidation that minimizes solvent and starting material loss through carbon burn. The process comprises oxidizing at least one oxidizable compound in an oxidizable raw material stream 30 in the presence of an oxidizing gas stream 10, solvent stream 20, and at least one catalyst system in a primary oxidation zone 125; wherein the oxidizable compound is selected from the group consisting of 5-(acetoxymethyl)furfural (5-AMF), 5-(ethoxymethyl)furfural (5-EMF), 5-methyl furfural (5-MF); wherein the solvent stream 20 comprises acetic acid with or without the presence of water; wherein the catalyst system comprising cobalt, manganese and bromine, wherein the weight ratio of cobalt to manganese in the reaction mixture ranges from about 10 to about 400 and the weight ratio of cobalt to bromine is from about 0.7 to about 3.5. The catalyst system with improved Co:Mn ratio can lead to high yield of FDCA. In this process, the oxidation temperature can vary from about 100° C. to about 220° C., or from about 110° C. to about 160° C. to minimize carbon burn. The cobalt concentration in the catalyst system can range from about 500 ppm to about 6000 ppm, and the amount of manganese from about 2 ppm to about 600 ppm and the amount of bromine from about 300 ppm to about 4500 ppm with respect to the total weight of the liquid in the reaction medium. Mixed feedstocks of 5-AMF and 5-HMF or 5-EMF and 5-HMF or 5-MF and 5-HMF or 5-AMF, 5-EMF and 5-HMF, with varying ratios of the components can be used and similar results can be obtained.

In another embodiment of the invention, a process is provided for producing furan-2,5-dicarboxylic acid (FDCA) in high yields by liquid phase oxidation that minimizes solvent and starting material loss through carbon burn. The process comprises oxidizing at least one oxidizable compound in an oxidizable raw material stream 30 in the presence of an oxidizing gas stream 10, solvent stream 20, and at least one catalyst system in a primary oxidation zone 125; wherein said oxidizable compound is 5-(hydroxymethyl)furfural (5-HMF); wherein said solvent stream comprises acetic acid with or without the presence of water; wherein said catalyst system comprising cobalt, manganese and bromine, wherein the weight ratio of cobalt to manganese in the reaction mixture is from about 10 to about 400. In this process, the temperature can vary from about 100° C. to about 220° C., from about 105° C. to about 180° C., and from about 110° C. to about 160° C. The cobalt concentration of the catalyst system can range from about 1000 ppm to about 6000 ppm, and the amount of manganese can range from about 2 ppm to about 600 ppm, and the amount of bromine can range from about 300 ppm to about 4500 ppm with respect to the total weight of the liquid in the reaction medium.

In another embodiment of the invention, the process comprises oxidizing at least one oxidizable compound in an oxidizable raw material stream 30 in the presence of an oxidizing gas stream 10, solvent stream 20, and at least one catalyst system in a primary oxidation zone 125; wherein said oxidizable compound is 5-(hydroxymethyl)furfural (5-HMF); wherein said solvent stream comprises a saturated organic acid having from 2-6 carbon atoms with or without the presence of water at a temperature of 100° C. to 220° C. to produce a dicarboxylic acid composition; wherein the primary oxidation zone 125 comprises at least one primary oxidation reactor and wherein the catalyst system comprises cobalt in a range from about 500 ppm by weight to about 6000 ppm by weight with respect to the weight of the liquid in the reaction medium, manganese in an amount ranging from about 2 ppm by weight to about 600 ppm by weight with respect to the weight of the liquid in the reaction medium and bromine in an amount ranging from about 300 ppm by weight to about 4500 ppm by weight with respect to the weight of the liquid in the reaction medium.

In another embodiment of the invention, when the oxidizable raw material stream 30 comprises 5-HMF, then the cobalt to manganese ratio by weight is at least 10:1, 15:1, 20:1, 25:1, 30:1, 40:1 50:1, 60:1, or 400 to 1.

In another embodiment of the invention, when the oxidizable material stream 30 comprises at least one oxidizable compound selected from the group consisting of 5-HMF esters (5-R(CO)OCH₂-furfural where R=alkyl, cycloalkyl and aryl), 5-HMF ethers (5-R′OCH₂-furfural, where R′=alkyl, cycloalkyl and aryl), 5-alkyl furfurals (5-R″-furfural, where R″=alkyl, cycloalkyl and aryl), mixed feedstocks of 5-HMF and 5-HMF esters, mixed feedstocks of 5-HMF and 5-HMF ethers, and mixed feed-stocks of 5-HMF and 5-alkyl furfurals, the cobalt to manganese ratio by weight of the catalyst system is at least 1:1, 10:1, 20:1, 50:1, 100:1, or 400:1.

In another embodiment of this invention, furan-2,5-dicarboxylic acid (FDCA) can be obtained by liquid phase oxidation of 5-(hydroxymethyl)furfural (5-HMF), 5-(acetoxymethyl)furfural (5-AMF) and 5-(ethoxymethyl)furfural (5-EMF) with molecular oxygen using Co/Mn/Br catalyst system in acetic acid solvent. After the oxidation of 5-HMF/5-AMF/5-EMF in presence of acetic acid, the FDCA precipitates out of solution. After filtration, washing with acetic acid and then with water, and drying, solids were obtained with a minimum of 90%, 92%, 94%, 96% FDCA content by weight.

In another embodiment of the invention, FDCA is obtained by liquid phase oxidation of 5-HMF, 5-AMF and 5-EMF with molecular oxygen using Co/Mn/Br catalyst system in acetic acid solvent. After the oxidation of 5-HMF/5-AMF/5-EMF in acetic acid, the FDCA precipitates out of solution. After filtration, washing with acetic acid and then with water, and drying, solids were obtained with a minimum of 96% FDCA content and a maximum b* of 15, 16, 17, 18, 19, or 20.

The b* is one of the three-color attributes measured on a spectroscopic reflectance-based instrument. The color can be measured by any device known in the art. A Hunter Ultrascan XE instrument is typically the measuring device. Positive readings signify the degree of yellow (or absorbance of blue), while negative readings signify the degree of blue (or absorbance of yellow).

In another embodiment of the invention, a process is provided for producing furan-2,5-dicarboxylic acid (FDCA) in minimum yields of 80% or 85% or 90% or greater by liquid phase oxidation that minimizes solvent and starting material loss through carbon burn. As used herein, yield is defined as mass of FDCA obtained divided by the theoretical amount of FDCA that should be produced based on the amount of raw material use. For example, if one mole or 126.11 grams of 5-HMF are oxidized, it would theoretically generate one mole or 156.01 grams of FDCA. If for example, the actual amount of FDCA formed is only 150 grams, the yield for this reaction is calculated to be =(150/156.01) times 100, which equals a yield of 96%. The same calculation applies for oxidation reaction conducted using 5-HMF derivatives or mixed feeds.

In another embodiment of this invention, a process is provided comprising oxidizing at least one oxidizable compound in an oxidizable raw material stream 30 in the presence of an oxidizing gas stream 10, solvent stream 20, and at least one catalyst system in a primary oxidation zone 125; wherein said oxidizable compound is selected from the group consisting of H(C═O)—R—(C═O)H, HOH2C—R—(C═O)H, 5-(hydroxymethyl)furfural (5-HMF); wherein said solvent stream comprises acetic acid with or without the presence of water; wherein said catalyst system comprises cobalt, manganese and bromine, wherein the weight ratio of cobalt to manganese in the reaction mixture is from about 10 to about 400 and the weight ratio of cobalt to bromine is from about 0.7 to about 3.5. Such a catalyst system with improved Co:Mn and Co:Br ratio can lead to high yield of FDCA (minimum of 90%), decrease in the formation of impurities (measured by b*) causing color in the downstream polymerization process while keeping the amount of CO and CO₂ in the off-gas at a minimum.

The temperature in the primary oxidation zone can range from about 100° C. to about 220° C., and can range from about 110° C. to about 160° C. or can range from about 105° C. to about 180° C. or about 100° C. to about 200° C., or about 100° C. to about 190° C. One advantage of the disclosed primary oxidation conditions is low carbon burn as illustrated in Table 1. Oxidizer off gas stream 120 is routed to the oxidizer off gas treatment zone 825 to generate an inert gas stream 810, liquid stream 820 comprising water, and a recovered solvent stream 830 comprising condensed solvent. In one embodiment, at least a portion of recovered solvent stream 830 is routed to wash fed stream 620 and the combined stream is routed to the solid-liquid separation zone 625 for the purpose of washing the solids present in the solid-liquid separation zone 625. In one embodiment, the inert gas stream 810 can be vented to the atmosphere. In another embodiment, at least a portion of the inert gas stream 810 can be used as an inert gas in the process for inerting vessels and or used for conveying gas for solids in the process.

In another embodiment of the invention, the composition of the liquid phase within the primary oxidizer can have a pH from about −4.0 to about 1.0 or the feedstock pH is from about −1.8 to about 1.0, or the feedstock pH is from about −1.5 to about 1.0.

It should be understood that steps (b)-(g) are optional and only one possible embodiment of a process to purified the carboxylic acid composition.

-   Step (b) comprises routing the crude carboxylic composition 110 and     fresh solvent stream 220 to a liquid displacement zone 225 to     produce a displaced mother liquor stream 230 and low impurity slurry     stream 210 comprising FDCA. The displaced mother liquor stream 230     comprises solvent and soluble matter dissolved in the solvent     comprising dissolved impurities and dissolved catalyst. In various     embodiments of the invention, from about 5% to about 99%, from about     30% to about 90%, and most preferably from about 50 to about 85% of     mother liquor present in the carboxylic acid composition 110 is     displaced in the liquid displacement zone 225 resulting in dissolved     matter comprising impurities present in the displaced mother liquor     not going forward in the process. Sufficient fresh solvent is fed to     the liquid displacement zone 225 that becomes mixed with solids     present resulting in a low impurity slurry stream 210 being pumpable     with weight % solids ranging from 1% to 50%, 10% to 40%, and     preferably the weight % solids in stream 210 will range from 25% to     38%.

The liquid displacement zone may be a single unit operation or multiple unit operations. In one embodiment of the invention, the liquid displacement zone 225 may be any solid-liquid separation device capable of generating an isolated wet cake from a feed slurry and then mixing the isolated wet cake with fresh solvent in a separate mixing device to generate the low impurity slurry stream 210. Examples of suitable solid-liquid separation devices include, but are not limited to, a continuous pressure drum filter, solid bowl centrifuges including, but not limited to, decanter and disc stack centrifuges, and batch pressure filters including, but not limited to, candle and leaf filters. The preferred solid-liquid separation device for this application is a continuous pressure drum filter. The solid-liquid separator is operated at temperatures between about 30 degrees C. to about 200 degrees C., preferably 80 degrees C. to about 170.degree.C. The solid-liquid separator in the liquid displacement zone 225 may be operated in continuous or batch mode, although it will be appreciated that for commercial processes, the continuous mode is preferred. Alternatively, a portion of the mother liquor in stream 110 is displaced with fresh liquor stream 220 in a single device to form the low impurity slurry stream 210 without forming an isolated wet cake.

In one embodiment, from 5% to 100% by weight of the displaced mother liquor stream 230 is routed to a purge zone 235 wherein a portion of the impurities present in stream 230 are isolated and exit the process as purge stream 920, wherein a portion is 5% by weight or greater. Recovered solvent stream 910 comprises solvent and catalyst isolated from stream 230 and is recycled to the process. In one embodiment, recovered solvent stream 910 is recycled to the primary oxidation zone 125 and contains greater than 30% of the catalyst that entered the purge zone 235 in stream 230. In another embodiment, stream 910 is recycled to the primary oxidation zone 125 and contains greater than 50 weight %, contains greater than 70 weight %, and preferably greater than 90 weight % of the catalyst that enters the purge zone 235 in stream 230 on a continuous or batch basis.

In another embodiment of this invention, a portion up to 100% of the carboxylic acid composition 110 may be routed directly to a secondary oxidation zone 335 without being subjected to the liquid displacement zone 225. In another embodiment of the invention, up to 100% of the feed to the purge zone 235 may be a mother liquor stream 630 generated in a solid-liquid separation zone 625 which also produces the purified wet cake stream 610.

In yet another embodiment, up to 100% of the feed to the purge zone 235 may be mother liquor generated in a secondary liquid displacement zone located at some location downstream of the secondary oxidation zone 325. A secondary liquid displacement zone is not show in FIG. 1, and it comprises equipment like that described for the liquid displacement zone 225 located after the primary oxidation zone 125, and must be located after the secondary oxidation zone 335.

-   Step (c) comprises oxidizing the low impurity slurry stream 210 in a     secondary oxidation zone 335 to form a purified slurry stream 310.     In one embodiment of the invention, the low impurity slurry stream     210 is routed to a secondary oxidation zone 335 where it is heated     to between about 115 degrees C. and about 220 degrees C., and     preferably between about 120 degrees C. to about 200 degrees C. and     further oxidized with an oxidizing gas, such as air, fed by line 320     to produce a purified slurry stream 310. The secondary oxidation     zone comprises at least one oxidation reactor vessel. In one     embodiment, the secondary oxidation zone can be one or more     oxidation vessels. When the carboxylic acid in low impurity slurry     stream 210 is FDCA, the secondary oxidation zone is operated at a     temperature ranging from about 115 degrees C. to about 220 degrees     C., preferably between about 120 degrees C. to about 200 degrees C.,     and stream 210 is further oxidized with an oxidizing gas stream fed     by line 320 to produce a purified slurry stream 310.

Generally, oxidation in the secondary oxidation zone 335 is at a higher temperature than the oxidation in the primary oxidation zone 125 to enhance the impurity removal. In one embodiment, the secondary oxidation zone 335 is operated at about 30° C., 20° C., and preferably 10° C. higher temperature than the oxidation temperature in the primary oxidation zone 125 to enhance the impurity removal. The secondary oxidation zone 335 can be heated directly with solvent vapor, or steam via stream 320 or indirectly by any means known in the art.

Additional purification of the low impurity slurry stream 210 is accomplished in the secondary oxidation zone by a mechanism involving recrystallization or crystal growth and oxidation of impurities and intermediates including FFCA. One of the functions of the secondary oxidation zone is to convert FFCA to FDCA. FFCA is considered monofunctional relative to a polyester condensation reaction because it contains only one carboxylic acid. FFCA is present in the carboxylic acid composition stream 110 and the low impurity slurry stream 210. FFCA is generated in the primary oxidation zone 125 because the reaction of 5-HMF to FFCA can be about eight times faster than the reaction of FFCA to the desired di-functional product FDCA. Additional air or molecular oxygen may be fed in stream 320 to the secondary oxidation zone 335 in an amount necessary to oxidize a substantial portion of the partially oxidized products such as FFCA in the stream 210 to the corresponding carboxylic acid FDCA. Generally, at least 70% by weight of the FFCA present in the low impurity slurry stream 210 is converted to FDCA in the secondary oxidation zone 335. Preferably, at least 80% by weight of the FFCA present in the low impurity slurry stream 210 is converted to FDCA in the secondary oxidation zone 335, and most preferably, at least 90% by weight of the FFCA present in the low impurity slurry stream 210 is converted to FDCA in the secondary oxidation zone 335. Significant concentrations of monofunctional molecules like FFCA in the dried, purified FDCA product are particularly detrimental to polymerization processes as they may act as chain terminators during the polyester condensation reaction.

The amount of oxygen fed in the secondary oxidation zone 335 in controlled to limit the burning of organic molecules to CO₂. The amount of oxygen in stream 330 is monitored and used to control the amount of oxygen fed in stream 320. Another function of the secondary oxidation zone 335 is to dissolve and recrystallize solids present in the low impurity slurry stream 210 fed to the secondary oxidation zone. At least 10% by weight, 25% by weight, 50% by weight, and preferably at least 85% by weight of solid impurities and oxidation by-products in stream 210 feed to the secondary oxidation zone 335 go into solution as the FDCA particles are dissolved and re-crystallized in the secondary oxidation zone 335. Off gas from the secondary oxidation zone is withdrawn via line 330 and fed to a recovery system where the solvent is removed from the off gas comprising volatile organic compounds (VOCs). VOCs including methyl bromide may be treated, for example by incineration in a catalytic oxidation unit. The purified slurry stream 310 generated in the secondary oxidation zone is routed to the crystallization zone 425.

-   Step (d) comprises crystallizing the secondary oxidation slurry 310     in a crystallization zone 425 to form a crystallized slurry stream     410. Generally, the crystallization zone 425 comprises at least one     crystallizer. Vapor from the crystallization zone can be condensed     in at least one condenser and returned to the crystallization zone     425 or routed away from crystallization zone 425. Optionally, the     liquid from the condenser or vapor product from the crystallization     zone can be recycled, or it can be withdrawn or sent to an energy     recovery device. In addition, the crystallizer off gas is removed     via line 420 and can be routed to a recovery system where the     solvent is removed, and crystallizer off gas comprising VOCs may be     treated, for example, by incineration in a catalytic oxidation unit.     When the carboxylic acid is FDCA, the purified slurry stream 310     from the secondary oxidation zone 335 is fed to a crystallization     zone 425 comprising at least one crystallizer where it is cooled to     a temperature between about 40.degrees C. to about 175 degrees C. to     form a crystallized slurry stream 410, preferably to a temperature     between about 50 degrees C. to about 170 degrees C., and most     preferably from about 60 degrees C. to about 165 degrees C.

The crystallized slurry stream 410 is then routed to a cooling zone 430 to generate a cooled crystallized slurry stream 510. The cooling of the crystallized slurry stream 410 can be accomplished by any means known in the art. Typically, the cooling zone 430 comprises a flash tank. The temperature of stream 510 can range from 35° C. to 160° C., 45° C. to 120° C., and preferably from 55° C. to 95° C.

In another embodiment, a portion of up to 100% of the secondary oxidation slurry stream 310 is routed directly to the cooling zone 425, thus the portion is not subjected to a crystallization zone 430. In yet another embodiment, a portion of up to 100% of the crystallized slurry stream 410 is routed directly to a secondary liquid displacement zone which is not illustrated in FIG. 1. Up to 100% of the slurry effluent comprising FDCA from a secondary liquid displacement zone can be routed to the solid-liquid separation zone 625 and or routed directly to the cooling zone 430. The function of the secondary liquid displacement zone is to displace a portion of solvent in the crystallized slurry stream 410 with fresh solvent and or water wherein a portion must be greater than 5 weight percent. The secondary liquid displacement zone is separate and distinct from the liquid displacement zone 225 located after the primary oxidation zone 125. The same type of equipment may be used for both the primary and secondary liquid displacement zones. In yet another embodiment, crystallized slurry stream 410 can be routed directly to the solid-liquid separation zone 625 without being first processed in the cooling zone 430.

-   Step (e) comprises isolating, washing, and dewatering solids present     in the cooled, crystallized slurry stream 510 in the solid-liquid     separation zone 625. These functions may be accomplished in a single     solid-liquid separation device or multiple solid-liquid separation     devices. The solid-liquid separation zone 625 comprises at least one     solid-liquid separation device capable of separating solids and     liquids, washing solids with a wash solvent stream 620, and reducing     the % moisture in the washed solids to less than 30 weight %, less     than 25 weight %, less than 20 weight %, less than 15 weight %, and     preferably less than 10 weight %.

Equipment suitable for the solid liquid separation zone 625 can typically be comprised of, but not limited to, the following types of devices: centrifuges, cyclones, rotary drum filter, belt filters, pressure leaf filters, candle filters, etc. The preferred solid liquid separation device for the solid liquid separation zone 625 is a rotary pressure drum filter. The temperature of the cooled, crystallized slurry steam 510 which is routed to the solid-liquid separation zone 625 can range from 50° C. to 140° C., 70° C. to 120° C., and is preferably from 75° C. to 95° C. The wash solvent stream 620 comprises a liquid suitable for displacing and washing mother liquor from the solids.

In one embodiment of the invention, a suitable wash solvent comprises acetic acid and water. In another embodiment, a suitable solvent comprises water up to 100% water. The temperature of the wash solvent can range from 20° C. to 135° C., 40° C. and 110° C., and preferably from 50° C. to 90° C. The amount of wash solvent used is defined as the wash ratio and equals the mass of wash divided by the mass of solids on a batch or continuous basis. The wash ratio can range from about 0.3 to about 5, about 0.4 to about 4, and preferably from about 0.5 to 3.

After solids are washed in the solid liquid separation zone, they are dewatered. Dewatering involves reducing the mass of moisture present with the solids to less than 30% by weight, less than 25% by weight, less than 20% by weight, less than 15% by weight, and most preferably less than 10% by weight resulting in the generation of a purified wet cake stream 610. In one embodiment, dewatering is accomplished in a filter by passing a gas stream through the solids to displace free liquid after the solids have been washed with a wash solvent. In another embodiment, dewatering is achieved by centrifugal forces in a perforated bowl or solid bowl centrifuge. Stream 630 generated in the solid-liquid separation zone 625 is a mother liquor stream comprising oxidation solvent, catalyst, and some impurities and oxidation byproducts. In one embodiment, a portion of stream 630 is routed to a purge zone 235 and a portion is routed back to the primary oxidation zone 125 wherein a portion is at least 5 weight %. Wash liquor stream 640 is also generated in the solid-liquid separation zone 625 and comprises a portion of the mother liquor present in stream 510 and wash solvent wherein the ratio of mother liquor mass to wash solvent mass is less than 3 and preferably less than 2.

-   Step (f) comprises drying the purified wet cake stream 610 in a     drying zone 725 to generate a dry purified carboxylic acid 710 and a     vapor stream 720. In one embodiment, vapor stream 720 comprises wash     solvent vapor. In another embodiment, vapor stream 720 comprises     oxidation solvent and wash solvent. The drying zone 725 comprises at     least one dryer and can be accomplished by any means known in the     art that is capable of evaporating at least 10% of the volatiles     remaining in the purified wet cake stream 610 to produce the dried,     purified carboxylic acid 710 comprising purified FDCA and a vapor     stream 720. For example, indirect contact dryers include, but are     not limited to, a rotary steam tube dryer, a Single Shaft     Porcupine_(RTM) dryer, and a Bepex Solidaire_(RTM) dryer. Direct     contact dryers include, but are not limited to, a fluid bed dryer     and drying in a convey line can be used for drying to produce stream     710. The dried, purified carboxylic acid 710 comprising purified     FDCA can be a carboxylic acid composition with less than 8%     moisture, preferably less than 5% moisture, and more preferably less     than 1% moisture, and even more preferably less than 0.5%, and yet     more preferably less than 0.1%. In another embodiment of this     invention, if the liquid portion of the purified wet cake stream 610     comprises water and contains less than 0.1 weight % acetic acid,     less than 500 ppm wt acetic acid, and preferably less than 200 ppm     wt, the stream 610 can be fed directly to a polymerization zone     without first being dried.

In one embodiment of the invention, a vacuum system can be utilized to draw vapor stream 720 from the drying zone 725. If a vacuum system is used in this fashion, the pressure of stream 720 at the dryer outlet can range from about 760 mmHg to about 400 mmHg, from about 760 mmHg to about 600 mmHg, from about 760 mmHg to about 700 mmHg, from about 760 mmHg to about 720 mmHg, and from about 760 mmHg to about 740 mmHg wherein pressure is measured in mmHg above absolute vacuum. The contents of the conduit between solid-liquid separation zone 625 and drying zone 725 utilized to transfer the purified wet cake stream 610 comprises wet cake stream and gas wherein gas is the continuous phase. The pressure at the exit of the solid liquid separation zone 625 can be close to that of the pressure where vapor stream 720 exits the drying zone 725, wherein close is defined as within 2 psig, within 0.8 psig, and preferably within 0.4 psig.

In an embodiment of the invention, the dried, purified carboxylic acid 710 has a b* less than about 9.0. In another embodiment of the invention, the b* color of the dried, purified carboxylic acid 710 is less than about 6.0. In another embodiment of the invention, the b* color of the dried, purified carboxylic acid 710 is less than about 5.0. In another embodiment of the invention, the b* color of the dried, purified carboxylic acid 710 is less than about 4.0. In another embodiment of the invention, the b* color of the dried, purified carboxylic acid 710 is less than about 3. The b* color is one of the three-color attributes measured on a spectroscopic reflectance-based instrument. A Hunter Ultrascan XE instrument in reflectance mode is typically the measuring device. Positive readings signify the degree of yellow (or absorbance of blue), while negative readings signify the degree of blue (or absorbance of yellow).

It should be appreciated that the process zones previously described can be utilized in any other logical order to produce the dried, purified carboxylic acid 710. It should also be appreciated that when the process zones are reordered that the process conditions may change. It is also understood that all percent values are weight percents.

-   Step (g) is an optionally step comprising decolorizing the FDCA in     this process or an esterified FDCA with a diol stream via     hydrogenation. In one embodiment, the diol stream comprises ethylene     glycol. In another embodiment, the diol stream comprises isomers of     cyclohexane diol, preferably the 1-4 cyclohexane diol isomer. The     decolorizing of the FDCA in this process or an esterified FDCA can     be accomplished by any means known in the art and is not limited to     hydrogenation. However, for example, in one embodiment of the     invention, the decolorizing can be accomplished by reacting a     carboxylic acid that has undergone esterification treatment, for     example with ethylene glycol, with molecular hydrogen in the     presence of a hydrogenation catalyst in a reactor zone to produce a     decolorized carboxylic acid solution or a decolorized ester product.

For the reactor zone, there are no special limitations in the form or construction thereof, subject to an arrangement that allows supply of hydrogen to effect intimate contact of the carboxylic acid or ester product with the catalyst in the reactor zone. Typically, the hydrogenation catalyst is usually a single Group VIII metal or combination of Group VIII metals. Preferably, the catalyst is selected from a group consisting of palladium, ruthenium, rhodium and combination thereof. The reactor zone comprises a hydrogenation reactor that operates at a temperature and pressure sufficient to hydrogenate a portion of the characteristically yellow compounds to colorless derivatives.

Since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit this invention to the exact process and operations illustrated and described above, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention

EXAMPLES

This invention can be further illustrated by the following examples of embodiments thereof, although it will be understood that these examples are included merely for the purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

Examples Set 1

In Examples 1a-3d, glacial acetic acid and the catalyst components in concentrations described in Tables 1, 2 and 3 were transferred to a 300 mL titanium autoclave equipped with a high pressure condenser, a baffle and an Isco pump. Cobalt, manganese and ionic bromine were provided as cobalt (II) acetate tetrahydrate, manganese (II) acetate and sodium bromide and/or aqueous hydrobromic acid respectively. The autoclave was pressurized with approximately 50 psig of nitrogen and the homogeneous mixture was heated to the desired temperature in a closed system (i.e., with no gas flow) with stirring. At reaction temperature, an air flow of 1500 sccm was introduced at the bottom of the solution and the reaction pressure was adjusted to the desired pressure. A solution of 5-HMF/5-AMF/5-EMF in acetic acid was fed to the mixture at a rate of 0.833 mL/min via a high pressure Isco pump (this is t=0 for the reaction time). After 30 seconds from the start of substrate feeding, 1.0 g of peracetic acid in 5.0 mL of acetic acid was introduced using a blow-case to start the reaction. The feed was stopped after 1 h and the reaction continued for an additional hour at the same conditions of air flow, temperature and pressure. After the reaction time was completed, the air flow was stopped and the autoclave was cooled to room temperature and depressurized. The heterogeneous mixture was filtered to isolate the crude FDCA. The mass of the filtrate was recorded. The crude FDCA was washed with 60 mL of acetic acid two times and then twice with 100 mL of DI water. The washed crude FDCA was oven dried at 110° C. under vacuum overnight and then weighed. The solid and the filtrate were analyzed by Gas Chromatography using BSTFA derivatization method.

The Off-gas was analyzed for CO and CO₂ by ND-1R (ABB, Advanced Optima) and O₂ by a paramagnetism detection system (Servomex, 1440 Model).

Analytical

Gas Chromatographic Method Process samples were analyzed using a Shimadzu gas chromatograph Model 2010 (or equivalent) equipped with a split/heated injector (300° C.) and a flame ionization detector (300° C.). A capillary column (60 meter×0.32 mm ID) coated with (6% cyanopropylphenyl)-methylpolysiloxane at 1.0 μm film thickness (such as DB-1301 or equivalent) was employed. Helium was used as the carrier gas with an initial column head pressure of 29.5 psi and an initial column flow of 3.93 mL/minute while the carrier gas linear velocity of 45 cm/second was maintained constant throughout the entire oven temperature program. The column temperature was programmed as follows: The initial oven temperature was set at 80° C. and was held for 6 minutes, the oven was ramped up to 150° C. at 4° C./minute and was held at 150° C. for 0 minute, the oven was ramped up to 240° C. at 10° C./minute and was held at 240° C. for 5 minutes, then the oven was ramped up to 290° C. at 10° C./minute and was held at 290° C. for 17.5 minutes (the total run time was 60 mins). 1.0-μl of the prepared sample solution was injected with a split ratio of 40:1. EZ-Chrom Elite chromatography data system software was used for data acquisition and data processing. The sample preparation was done by weighing 0.1 g (accurate to 0.1 mg) of sample in a GC vial and adding 200.0 μl ISTD solution (1% by volume of decane in pyridine) and 1000 μl of BSTFA (N, O-bis(trimethylsilyl) trifluoroacetamide) with 1% TMSCl (trimethylchlorosilane) to the GC vial. The content was heated at 80° C. for 30 minutes to ensure complete derivatization. 1.0-μl of this prepared sample solution was injected for GC analysis.

-   Color measurement. 1) Assemble the Carver Press die as instructed in     the directions—place the die on the base and place the bottom 40 mm     cylinder polished side face-up. -   2) Place a 40 mm plastic cup (Chemplex Plasticup, 39.7×6.4 mm) into     the die. -   3) Fill the cup with the sample to be analyzed. The exact amount of     sample added is not important. -   4) Place the top 40 mm cylinder polished side face-down on the     sample. -   5) Insert the plunger into the die. No “tilt” should be exhibited in     the assembled die. -   6) Place the die into the Carver Press, making sure that it is near     the center of the lower platen. Close the safety door. -   7) Raise the die until the upper platen makes contact with the     plunger. Apply >20,000 lbs pressure. Then allow the die to remain     under pressure for approximately 3 minutes (exact time not     critical). -   8) Release the pressure and lower the lower platen holding the die. -   9) Disassemble the die and remove the cup. Place the cup into a     labeled plastic bag (Nasco Whirl-Pak 4 oz). -   10) Using a HunterLab Colorquest XE colorimeter, create the     following method (Hunterlab EasyQuest QC software, version 3.6.2 or     later)     Mode: RSIN-LAV (Reflectance Specular Included-Large Area View)     Measurements: -   CIE L* a* b* -   CIE X Y Z -   11) Standardize the instrument as prompted by the software using the     light trap accessory and the certified white tile accessory pressed     against the reflectance port. -   12) Run a green tile standard using the certified white tile and     compare the CIE X, Y, and Z values obtained against the certified     values of the tile. The values obtained should be ±0.15 units on     each scale of the stated values. -   13) Analyze the sample in the bag by pressing it against the     reflectance port and obtaining the spectrum and L*, a*, b* values.     Obtain duplicate readings and average the values for the report.     Interpretation of Results:

During the oxidation of 5-HMF to FDCA the alcohol site (ArCH₂OH) was converted into carboxylic acid (ArCOOH) mainly via aldehyde (ArCHO), eq 3. Examples 1a, and 1b (Table-1) which use catalyst systems consisting of cobalt, manganese and aqueous hydrobromic acid source produced about 90% yield of FDCA with >98% purity of crude FDCA solid and with a b* of about 6. The crude FDCA solid also contains 5-Formylfuran-2-carboxylic acid (FFCA), only the hydroxylmethyl groups are oxidized to carboxylic acid groups, due to incomplete oxidation.

Oxidation of 5-AMF, which contains an oxidizable ester and aldehydes moieties, produced FDCA, FFCA, and acetic acid, eq 4. Examples 2a to 2b (Table-2) demonstrate that a minimum of 99% purity FDCA solid with a b* of about 7 or less can be achieved using cobalt, manganese and aqueous hydrobromic acid catalyst system.

Oxidation of 5-EMF, which contains an oxidizable ether and aldehyde moieties, produced FDCA, FFCA, 5-(ethoxycarbonyl)furan-2-carboxylic acid (EFCA) and acetic acid, eq 5. Examples 3a to 3d (Table-3) show that a minimum of 96% purity FDCA solid with a b* of about 6 or less can be achieved using cobalt, manganese and aqueous hydrobromic acid catalyst system.

It is very important to note that in a continuous process under the same conditions as described in this invention report (which was conducted as a batch process) even higher purity of crude FDCA is expected due to efficient mixing, relatively low concentrations of reactive intermediates, and other reasons familiar to those skilled in the art.

TABLE 1 Results from semi-batch reactions performed as described above using 5-HMF feed.* Mn conc Br conc Temp yield of FDCA yield of FFCA Solid Composition Example Co conc (ppm) (ppm) (ppm) (° C.) (%) (%) FDCA FFCA b* 1a 2000 93.3 3000 132 89.4 0.58 99.20 0.81 5.845 1b 2000 93.3 3000 132 88.6 0.8 98.67 0.77 6.175 *P = 130 psig.

TABLE 2 Results from semi-batch reactions performed as described above using 5-AMF feed.* Mn conc Br conc Temp yield of FDCA yield of FFCA Solid Composition Example Co conc (ppm) (ppm) (ppm) (° C.) (%) (%) FDCA FFCA b* 2a 2500 116.8 2500 130 88.2 0.25 99.71 0.25 4.4 2b 2000 93.5 3000 130 90.2 0.16 99.44 0.16 6.8 *P = 130 psig.

TABLE 3 Results from semi-batch reactions performed as described above using EMF feed.* Co conc Mn conc Br conc Temp yield of FDCA yield of FFCA yield of EFCA Solid Composition Example (ppm) (ppm) (ppm) (° C.) (%) (%) (%) FDCA FFCA EFCA b* 3a 2500 116.8 2500 130 89.0 0.02 0.23 99.04 0.02 0.02 3.97 3b 2500 116.8 2500 130 87.4 0.42 1.31 98.08 0.42 0.04 2.74 3c 2000 93.5 3000 130 88.0 0.09 0.43 99.20 0.09 0.05 5.845 3d 2000 93.5 3000 105 86.0 2.92 1.40 96.22 2.90 0.15 0.98 *P = 130 psig.

Examples Set 2

Air oxidation of 5-HMF using cobalt, manganese and ionic bromine catalysts system in acetic acid solvent were conducted. After reaction the heterogeneous mixture was filtered to isolate the crude FDCA. The crude FDCA was washed with acetic acid two times and then twice with DI water. The washed crude FDCA was oven dried at 110° C. under vacuum overnight. The solid and the filtrate were analyzed by Gas Chromatography using BSTFA derivatization method. b* of the solid was measured using a Hunter Ultrascan XE instrument. As shown in Table 4 we have discovered conditions that to generate yields of FDCA up to 89.4%, b*<6, and low carbon burn (<0.0006 mol/min CO+CO₂)

TABLE 4 Results from semi-batch reactions.* Mn CO CO₂ pH, Bromide Co conc conc Br conc yield of yield of (total (total CO_(x) before color Example source (ppm) (ppm) (ppm) FDCA (%) FFCA (%) mol) mol) (mol/min) reaction (b*) 4a solid NaBr 2000 93.3 3000 81.6 0.81 0.013 0.078 0.000758 −0.12 13.91 4b solid NaBr 2000 93.3 3000 82.6 0.87 0.013 0.092 0.000875 −0.12 14.14 4c aqueous HBr 2000 93.3 3000 89.4 0.58 0.003 0.061 0.000533 −1.03 5.845 4d aqueous HBr 2000 93.3 3000 88.6 0.8 0.0037 0.061 0.000539 −1.03 6.175 *P = 130 psig, CO_(x) (mol/min) = CO (mol/min) + CO2 (mol/min).

Examples Set 3

In Examples 5a-5h, glacial acetic acid and the catalyst components in concentrations described in Table-5 were transferred to a 300 mL titanium autoclave equipped with a high pressure condenser, a baffle and an Isco pump. Cobalt, manganese and ionic bromine were provided as cobalt (II) acetate tetrahydrate, manganese (II) acetate and sodium bromide and/or aqueous hydrobromic acid respectively. The autoclave was pressurized with approximately 50 psig of nitrogen and then the homogeneous mixture was heated to the desired temperature in a closed system (i.e., with no gas flow) with stirring. At reaction temperature, an air flow of 1500 sccm was introduced at the bottom of the solution and the reaction pressure was adjusted to the desired pressure. A solution of 5-HMF in acetic acid was fed to the mixture at a rate of 0.833 mL/min via a high pressure Isco pump (this is t=0 for the reaction time). After 30 seconds from the start of 5-HMF feeding, 1.0 g of peracetic acid in 5.0 mL of acetic acid was introduced using a blow-case to start the reaction. The feed was stopped after 1 h and the reaction continued for 1 more hour at the same conditions of air flow, temperature and pressure. After the reaction time was completed the air flow was stopped and the autoclave was cooled to room temperature and depressurized. The heterogeneous mixture was filtered to isolate the crude FDCA. The mass of the filtrate was recorded. The crude FDCA was washed with 60 mL of acetic acid two times and then twice with 100 mL of DI water. The washed crude FDCA was oven dried at 110° C. under vacuum overnight and then weighed. The solid and the filtrate were analyzed by Gas Chromatography using BSTFA derivatization method.

The Off-gas was analyzed for CO and CO₂ by ND-1R (ABB, Advanced Optima) and O₂ by a paramagnetism detection system (Servomex, 1440 Model).

Analytical

Gas Chromatographic Method Process samples were analyzed using a Shimadzu gas chromatograph Model 2010 (or equivalent) equipped with a split/heated injector (300° C.) and a flame ionization detector (300° C.). A capillary column (60 meter×0.32 mm ID) coated with (6% cyanopropylphenyl)-methylpolysiloxane at 1.0 μm film thickness (such as DB-1301 or equivalent) was employed. Helium was used as the carrier gas with an initial column head pressure of 29.5 psi and an initial column flow of 3.93 mL/minute while the carrier gas linear velocity of 45 cm/second was maintained constant throughout the entire oven temperature program. The column temperature was programmed as follows: The initial oven temperature was set at 80° C. and was held for 6 minutes, the oven was ramped up to 150° C. at 4° C./minute and was held at 150 for 0 minute, the oven was ramped up to 240° C. at 10° C./minute and was held at 240 for 5 minutes, then the oven was ramped up to 290° C. at 10° C./minute and was held at 290 for 17.5 minutes (the total run time was 60 mins). 1.0-μl of the prepared sample solution was injected with a split ratio of 40:1. EZ-Chrom Elite chromatography data system software was used for data acquisition and data processing. The sample preparation was done by weighing 0.1 g (accurate to 0.1 mg) of sample in a GC vial and adding 200.0 μl ISTD solution (1% by volume of decane in pyridine) and 1000 μl of BSTFA (N,O-bis(trimethylsilyl)trifluoroacetamide) with 1% TMSCl (trimethylchlorosilane) to the GC vial. The content was heated at 80° C. for 30 minutes to ensure complete derivatization. 1.0-μl of this prepared sample solution was injected for GC analysis.

pH measurement. The electrode for determining non-aqueous pH and millivolts was a Schott N6480-eth series electrode. The LiCl/EtOH filling solution was replaced with (Et)₄N⁺Br/ethylene glycol. The electrode response was monitored by Multi-T 2.2 software through a Jensen Systems cdv-70 series Sensolab interface box. The buffers (pH 4 and 7) were purchased from VWR, and the (Et)₄N⁺Br⁻/ethylene glycol filling solution was from Metrohm.

To perform the pH measurements, a non-aqueous electrode was initially calibrated using aqueous buffers of 4 and 7 allowing the electrode to equilibrate with each for two to three minutes before calibrating at the respective level. Once the electrode was calibrated within 97.5% of 59.2 millivolts slope, the samples were portioned (˜15 mL) into smaller vials with mini-Teflon stir bars. The samples were then placed on a stir plate, and the electrode was lowered into the sample. The depth of the electrode was set to where the sample covered about half of the junction slide. Once the sample and electrode was ready, the sample was measured for non-aqueous pH over a period of three minutes. The time was sufficient for equilibration between the electrode and the sample. Between each sample measurement, the electrode was rinsed with Millipore-grade water and wiped with a Kimwipe. The results were recorded in non-aqueous pH units. The millivolts results were also recorded.

-   Color measurement. 1) Assemble the Carver Press die as instructed in     the directions—place the die on the base and place the bottom 40 mm     cylinder polished side face-up. -   2) Place a 40 mm plastic cup (Chemplex Plasticup, 39.7×6.4 mm) into     the die. -   3) Fill the cup with the sample to be analyzed. The exact amount of     sample added is not important. -   4) Place the top 40 mm cylinder polished side face-down on the     sample. -   5) Insert the plunger into the die. No “tilt” should be exhibited in     the assembled die. -   6) Place the die into the Carver Press, making sure that it is near     the center of the lower platen. Close the safety door. -   7) Raise the die until the upper platen makes contact with the     plunger. Apply >20,000 lbs pressure. Then allow the die to remain     under pressure for approximately 3 minutes (exact time not     critical). -   8) Release the pressure and lower the lower platen holding the die. -   9) Disassemble the die and remove the cup. Place the cup into a     labeled plastic bag (Nasco Whirl-Pak 4 oz). -   10) Using a HunterLab Colorquest XE colorimeter, create the     following method (Hunterlab EasyQuest QC software, version 3.6.2 or     later)     Mode: RSIN-LAV (Reflectance Specular Included-Large Area View)     Measurements: -   CIE L* a* b* -   CIE X Y Z -   11) Standardize the instrument as prompted by the software using the     light trap accessory and the certified white tile accessory pressed     against the reflectance port. -   12) Run a green tile standard using the certified white tile and     compare the CIE X, Y, and Z values obtained against the certified     values of the tile. The values obtained should be ±0.15 units on     each scale of the stated values. -   13) Analyze the sample in the bag by pressing it against the     reflectance port and obtaining the spectrum and L*, a*, b* values.     Obtain duplicate readings and average the values for the report.

Interpretation of Results:

Examples 5c, 5d, 5e and 5f (Table-5) which use catalyst systems consisting of cobalt, manganese and aqueous hydrobromic acid or aqueous hydrobromic acid and sodium bromide as a bromide source produced about 90% yield of FDCA, minimum colored impurities (measured by b*) and a minimum level of CO and CO₂ (CO_(X), mol/min) in the off-gas. One of the reasons for the differences in activity between hydrobromide and sodium bromide, in a single batch reaction, is due to faster oxidation of HBr by Mn(III), eq 6, than sodium bromide (it is about 22 times faster: Jiao, X. J.; Espenson, J. H. Inorg. Chem. 2000, 39, 1549). The activity of hydrobromic acid or sodium bromide reaction mediums can be increased by addition of a strong Brønsted acid (such as triflic acid, HCl, etc.). Mn(OAc)₃+2HBr→2HOAc+Mn(OAc)Br₂→Mn(OAc)₂+HBr₂ ^(•)—  (6)

Comparative examples 5g and 5h show the inhibiting effect of excess manganese. Therefore it is desirable to limit the amount of manganese, during the oxidation process, to achieve high yield of FDCA.

It is very important to note that in a continuous process under the same conditions as described in this invention report (conducted as a batch process) higher than 90% yield of FDCA expected due to efficient supply of oxygen and mixing.

TABLE 5 Results from semi-batch reactions performed as described above.* Co conc Mn conc Br conc yield of yield of CO (total CO₂ (total CO_(x) pH, before Example Bromide source (ppm) (ppm) (ppm) FDCA (%) FFCA (%) mol) mol) (mol/min) reaction color (b*) 5a solid NaBr 2000 93.3 3000 81.6 0.81 0.013 0.078 0.000758 −0.12 13.91 5b solid NaBr 2000 93.3 3000 82.6 0.87 0.013 0.092 0.000875 −0.12 14.14 5c aqueous HBr 2000 93.3 3000 89.4 0.58 0.003 0.061 0.000533 −1.03 5.845 5d aqueous HBr 2000 93.3 3000 88.6 0.8 0.0037 0.061 0.000539 −1.03 6.175 5e aqueous HBr + solid 2000 93.3 3000 91.7 0.96 0.008 0.07 0.000650 −0.63 8.185 NaBr 5f aqueous HBr + solid 2000 93.3 3000 90.2 0.87 0.008 0.072 0.000667 −0.63 7.95 NaBr 5g aqueous HBr 2000 2000 3000 79.4 1.08 0.009 0.072 0.000675 −0.84 6.21 5h aqueous HBr 2000 2000 3000 80.5 1.32 0.009 0.071 0.000667 −0.84 6.31 *T = 132 C., P = 130 psig. CO_(x) (mol/min) = CO (mol/min) + CO₂ (mol/min). FFCA = 5-Formylfuran-2-carboxylic acid.

Example Set 4

In Examples 1-34, 72, 73, 85, 86, 91, 92 and 93 glacial acetic acid and the catalyst components in concentrations described in the Tables 6 and 7 were transferred to a 300 mL titanium autoclave equipped with a high pressure condenser, a baffle and an Isco pump. Cobalt, manganese and ionic bromine were provided as cobalt (II) acetate tetrahydrate, manganese (II) acetate and sodium bromide/aqueous hydrobromic acid respectively. The autoclave was pressurized with approximately 50 psig of nitrogen and then the homogeneous mixture was heated to the desired temperature in a closed system (i.e., with no gas flow) with stirring. At reaction temperature, an air flow of 1500 sccm was introduced at the bottom of the solution and the reaction pressure was adjusted to the desired pressure. A solution of 5-HMF in acetic acid was fed to the mixture at a rate of 0.833 mL/min via a high pressure Isco pump (this is t=0 for the reaction time). After 30 seconds from the start of 5-HMF feeding, 1.0 g of peracetic acid in 5.0 mL of acetic acid was introduced using a blow-case to start the reaction. The feed was stopped after 1 h and the reaction continued for 1 more hour at the same conditions of air flow, temperature and pressure. After the reaction time was completed the air flow was stopped and the autoclave was cooled to room temperature and depressurized. The heterogeneous mixture was filtered to isolate the crude FDCA. The mass of the filtrate was recorded. The crude FDCA was washed with 60 mL of acetic acid two times and then twice with 100 mL of DI water. The washed crude FDCA was oven dried at 110° C. under vacuum overnight and then weighed. The solid and the filtrate were analyzed by Gas Chromatography using BSTFA derivatization method. A typical GC-chromatogram for isolated crude FDCA sample is shown in FIG. 2. The purity of this solid was confirmed by NMR spectroscopy, FIGS. 3 and 4.

The Off-gas was analyzed for CO and CO₂ by ND-1R (ABB, Advanced Optima) and O₂ by a paramagnetism detection system (Servomex, 1440 Model).

Analytical

Gas Chromatographic Method Process sample was analyzed using a Shimadzu gas chromatograph Model 2010 (or equivalent) equipped with a split/heated injector (300° C.) and a flame ionization detector (300° C.). A capillary column (60 meter×0.32 mm ID) coated with (6% cyanopropylphenyl)-methylpolysiloxane at 1.0 μm film thickness (such as DB-1301 or equivalent) was employed. Helium was used as the carrier gas with an initial column head pressure of 29.5 psi and an initial column flow of 3.93 ml/minute while the carrier gas linear velocity of 45 cm/second was maintained constant throughout the entire oven temperature program. The column temperature was programmed as follows: The initial oven temperature was set at 80° C. and was held for 6 minutes, the oven was ramped up to 150° C. at 4° C./minute and was held at 150 for 0 minute, the oven was ramped up to 240° C. at 10° C./minute and was held at 240 for 5 minute, then the oven was ramped up to 290° C. at 10° C./minute and was held at 290 for 17.5 minutes (the total run time was 60 mins). 1.0-μl of the prepared sample solution was injected with a split ratio of 40:1. EZ-Chrom Elite chromatography data system software was used for data acquisition and data processing. The sample preparation was done by weighing 0.1 g (accurate to 0.1 mg) of sample in a GC vial and adding 200.0 μl ISTD solution (1% by volume of decane in pyridine) and 1000 μl of BSTFA (N,O-bis(trimethylsilyl) trifluoroacetamide) with 1% TMSCl (trimethylchlorosilane) to the GC vial. The content was heated at 80° C. for 30 minutes to ensure complete derivatization. 1.0-μl of this prepared sample solution was injected for GC analysis.

Interpretation of Results:

Experiments 1-34, Table 6, were conducted by varying temperature, pressure and levels of cobalt and bromine concentrations to determine optimum conditions and catalyst compositions that produces very high yield of FDCA with minimum amount of carbon burn. In this invention, the weight ratio of cobalt to manganese was deliberately kept very high (i.e. 21) in all the reactions to avoid the inhibiting effect of excess manganese especially below 160° C.

As can be seen from FIG. 5, under the reaction conditions investigated in this invention the factor that has the most impact on the yield of FDCA is temperature. It is also important to note that the yield increases with increasing cobalt and bromine concentrations.

The data presented in Table 6 was used to develop a theoretical polynomial model to predict FDCA yield under different conditions, eq-7. Examples of predicted FDCA yields using this model is given in Table 7. Experiments No 72, 73, 85, and 86, Table 7, were conducted under the predicted conditions. As can be seen from the results they agree well with the predicted values within experimental error. % yield of FDCA=−91.469+2.83*T−0.01*P−0.02*[Co]+0.003*[Br]−0.01*T ²+3.9*10⁻⁶*[Co]²  (7)

Examples 91-93, Table 8, were conducted under the US patent applications (US200310055271 A1) conditions using our set-up. As can be seen from Tables 6, 7 and 8, the patent application conditions gave much inferior yield of FDCA than the current invention.

TABLE 6 Results from semi-batch reactions performed as described above.* C: Cobalt D: Br A: Temperature B: Pressure Conc Conc % % yield of % yield of CO CO2 CO_(x) Run deg, C. psi ppm ppm conversion FDCA FFCA (total mol) (total mol) (mol/min) 1 130 200 4000 1500 99.26 75.7 1.1 0.011 0.088 0.00083 2 155 450 3000 2250 99.1 67.3 0.08 0.032 0.163 0.00163 3 180 200 4000 3000 100 68.7 0.037 0.049 0.161 0.00175 4 180 700 2000 3000 98.57 57.3 0.0049 0.044 0.17 0.00178 5 180 200 2000 1500 94.47 48.3 0.96 0.044 0.125 0.00141 6 155 450 3000 2250 99.07 67.2 0.07 0.031 0.158 0.00158 7 130 700 4000 3000 100 78 0.34 0.017 0.183 0.00167 8 130 200 2000 3000 97.11 82.1 1.1 0.012 0.095 0.00089 9 180 700 4000 1500 99.5 53 0.02 0.053 0.148 0.00168 10 155 450 3000 2250 99.38 70.9 0.148 0.032 0.16 0.00160 11 130 700 2000 1500 99.84 68 0.79 0.024 0.168 0.00160 12 180 200 4000 1500 99.26 53.3 0.003 0.061 0.185 0.00205 13 155 450 3000 2250 100 70 0.2 0.03 0.158 0.00157 14 130 200 2000 1500 96.2 74.6 1.49 0.015 0.093 0.00090 15 130 200 4000 3000 99.57 85.3 0.7 0.009 0.083 0.00077 16 130 700 4000 1500 99.9 73.9 0.87 0.018 0.129 0.00123 17 155 450 3000 2250 100 71.2 0.1 0.03 0.159 0.00158 18 130 700 2000 3000 99.89 70.3 0.54 0.02 0.13 0.00125 19 180 200 2000 3000 99.5 58.4 0.464 0.058 0.0193 0.00064 20 180 700 2000 1500 100 54.3 0.55 0.053 0.175 0.00190 21 155 450 3000 2250 100 58.5 0.089 0.029 0.155 0.00153 22 180 700 4000 3000 100 60 0.025 0.048 0.158 0.00172 23 200 450 3000 2250 100 23 0 0.158 0.284 0.00368 24 200 450 3000 2250 100 23.8 0 0.156 0.266 0.00352 25 155 450 3000 2250 99.69 66.2 0.143 0.028 0.154 0.00152 26 155 50 3000 2250 99.05 79 0.075 0.019 0.109 0.00107 27 155 450 3000 1500 98.14 67.4 0.18 0.032 0.15 0.00152 28 155 950 3000 2250 99.94 62.8 0.118 0.034 0.164 0.00165 29 155 450 3000 2250 99.81 68.9 0.093 0.027 0.152 0.00149 30 105 450 3000 2250 97.12 66.9 3.56 0.013 0.099 0.00093 31 155 450 4000 2250 99.92 66.4 0.06 0.032 0.158 0.00158 32 155 450 3000 3750 100 68.8 0.178 0.026 0.151 0.00148 33 155 450 3000 2250 99.76 72 0.1 0.027 0.154 0.00151 34 155 450 2000 2250 99.89 70.3 0.54 0.02 0.13 0.00125 *Cobalt to manganese weight ratio = 21 for all experiments.

TABLE 7 Predicted yields of FDCA. 72, 73, 74, 85 and 86 are experimental results.* Pres- Cobalt Br yield of yield of Number Temperature sure Conc Conc FDCA FFCA 35 139 50 3999 3000 85.1504 0.447749 36 139 50 4000 2981 85.0945 0.442835 37 138 70 4000 3000 85.0502 0.469564 38 138 74 4000 3000 85.0244 0.473723 39 138 63 3988 3000 84.9913 0.463436 40 139 50 3999 2948 84.976 0.435265 41 139 50 4000 2938 84.9472 0.432597 42 139 50 3981 2973 84.9129 0.443582 43 138 51 3951 2999 84.7494 0.455411 44 138 50 3935 2999 84.629 0.455856 45 138 50 3917 3000 84.4874 0.458526 46 138 53 3917 3000 84.4716 0.461423 47 138 50 4000 2777 84.3976 0.406641 48 138 50 3905 2998 84.3893 0.45981 49 137 50 3881 3000 84.2031 0.463274 50 139 50 3886 3000 84.1187 0.428238 51 137 50 4000 2596 83.7624 0.395897 52 137 50 3992 2606 83.724 0.39788 53 136 50 3804 3000 83.6075 0.473555 54 136 51 3780 3000 83.4262 0.477259 55 137 227 3994 3000 83.3911 0.433817 56 137 50 4000 2386 82.9936 0.394841 57 135 50 3694 2946 82.6042 0.479136 58 135 50 4000 2166 82.2022 0.446345 59 136 50 4000 2152 82.1354 0.433632 60 131 61 2000 3000 81.8774 1.49331 61 131 59 2002 2993 81.8506 1.4836 62 131 59 2000 2986 81.8418 1.48296 63 131 55 2026 3000 81.7822 1.4441 64 130 83 2000 3000 81.5573 1.48713 65 132 50 2074 3000 81.5533 1.34737 66 130 91 2000 3000 81.4703 1.47787 67 130 89 2000 3000 81.4632 1.4882 68 132 50 2103 3000 81.3982 1.28915 69 131 50 2005 2833 81.2848 1.37298 70 139 51 4000 1973 81.2207 0.327309 71 132 130 2000 3000 81.1875 1.33938 72. 132 130 2000 3000 81.5 0.79 Experimental result.* 73. 132 130 2000 3000 81.6 0.81 Experimental result.* 74. 132 130 2000 3000 81.6 0.81 Experimental result.* 75 132 50 2144 3000 81.1813 1.21129 76 131 50 2146 2993 81.1115 1.22154 77 132 50 2160 3000 81.1035 1.18214 78 132 50 2001 2739 81.0004 1.30911 79 132 50 2000 2681 80.7904 1.28011 80 133 50 2228 2993 80.7581 1.06473 81 133 52 2000 2563 80.3266 1.22742 82 133 50 2000 2484 80.0491 1.2075 83 130 51 3136 3000 79.8341 0.591352 84 133 50 4000 1542 79.8127 0.750216 85 135 50 3066 3000 79.7967 0.503153 85. 135 50 3066 3000 85.3 0.86 Experimental result.* 86. 135 50 3066 3000 83.2 0.96 Experimental result.* 87 134 50 4000 1527 79.7531 0.668935 88 135 206 2262 3000 78.9815 0.792438 89 132 50 2000 2052 78.3528 1.25619 90 137 627 2000 3000 75.8366 0.489432 *Cobalt to Manganese weight ratio = 21 for all experiments.

TABLE 8 Reactions conducted using the patent application (US20030055271A1) conditions.^(a) C: Cobalt D: Br % % yield of % yield of CO2 (total CO_(x) Run A: Temperature B: Pressure Conc Conc conversion FDCA FFCA CO (total mol) mol) (mol/min) patent 125 950 406 1102 44.7 2.4 (US2003/0055271A1) 91^(b) 125 950 406 1102 98.42 40.1 2.3 0.03 0.128 0.00132 patent 100 950 406 1102 44.8 3.3 (US2003/0055271A1) 92^(b) 100 950 406 1102 60.51 0.5 4.4 0.005 0.028 0.00028 93^(b) 100 950 406 1102 64.33 0.9 2.7 0.005 0.031 0.00030 ^(a)Cobalt to Manganese ratio = 1. ^(b)Unknown peaks in the GC.

Examples Set 5

In Examples 9a-11b, glacial acetic acid and the catalyst components in concentrations described in Tables 9, 10 and 11 were transferred to a 300 mL titanium autoclave equipped with a high pressure condenser, a baffle and an Isco pump. Cobalt, manganese and ionic bromine were provided as cobalt (II) acetate tetrahydrate, manganese (II) acetate and aqueous hydrobromic acid respectively. The autoclave was pressurized with approximately 50 psig of nitrogen and the homogeneous mixture was heated to the desired temperature in a closed system (i.e., with no gas flow) with stirring. At reaction temperature, an air flow of 1500 sccm was introduced at the bottom of the solution and the reaction pressure was adjusted to the desired pressure. A solution of 5-MF/5-AMF/5-EMF in acetic acid was fed to the mixture at a rate of 0.833 mL/min via a high pressure Isco pump (this is t=0 for the reaction time). After 30 seconds from the start of substrate feeding, 1.0 g of peracetic acid in 5.0 mL of acetic acid was introduced using a blow-case to start the reaction. The feed was stopped after 1 h and the reaction continued for an additional hour at the same conditions of air flow, temperature and pressure. After the reaction time was completed, the air flow was stopped and the autoclave was cooled to room temperature and depressurized. The heterogeneous mixture was filtered to isolate the crude FDCA. The mass of the filtrate was recorded. The crude FDCA was washed with 60 mL of acetic acid two times and then twice with 100 mL of DI water. The washed crude FDCA was oven dried at 110° C. under vacuum overnight and then weighed. The solid and the filtrate were analyzed by Gas Chromatography using BSTFA derivatization method.

The off-gas was analyzed for CO and CO₂ by ND-1R (ABB, Advanced Optima) and O₂ by a paramagnetism detection system (Servomex, 1440 Model).

Analytical

Gas Chromatographic Method Process samples were analyzed using a Shimadzu gas chromatograph Model 2010 (or equivalent) equipped with a split/heated injector (300° C.) and a flame ionization detector (300° C.). A capillary column (60 meter×0.32 mm ID) coated with (6% cyanopropylphenyl)-methylpolysiloxane at 1.0 μm film thickness (such as DB-1301 or equivalent) was employed. Helium was used as the carrier gas with an initial column head pressure of 29.5 psi and an initial column flow of 3.93 mL/minute while the carrier gas linear velocity of 45 cm/second was maintained constant throughout the entire oven temperature program. The column temperature was programmed as follows: The initial oven temperature was set at 80° C. and was held for 6 minutes, the oven was ramped up to 150° C. at 4° C./minute and was held at 150° C. for 0 minute, the oven was ramped up to 240° C. at 10° C./minute and was held at 240° C. for 5 minutes, then the oven was ramped up to 290° C. at 10° C./minute and was held at 290° C. for 17.5 minutes (the total run time was 60 mins). 1.0-μl of the prepared sample solution was injected with a split ratio of 40:1. EZ-Chrom Elite chromatography data system software was used for data acquisition and data processing. The sample preparation was done by weighing 0.1 g (accurate to 0.1 mg) of sample in a GC vial and adding 200.0 μl ISTD solution (1% by volume of decane in pyridine) and 1000 μl of BSTFA (N, O-bis(trimethylsilyl)trifluoroacetamide) with 1% TMSCl (trimethylchlorosilane) to the GC vial. The content was heated at 80° C. for 30 minutes to ensure complete derivatization. 1.0-μl of this prepared sample solution was injected for GC analysis.

Interpretation of Results:

5-AMF Feed Studies:

Oxidation of 5-AMF, which contains an oxidizable ester and aldehydes moieties, produced FDCA, FFCA, and acetic acid, eq 8. Experiments 9a-9k, Table 9, were conducted by varying temperature, and levels of cobalt and bromine concentrations to determine optimum conditions and catalyst compositions that produces very high yield of FDCA with minimum amount of carbon burn. In this invention, the weight ratio of cobalt to manganese was deliberately kept very high (i.e. 21) in all the reactions to avoid the inhibiting effect of excess manganese especially below 160° C. Further discussion on mechanism of initiation and inhibition by Mn(II) in oxidation can be found in Zakharov, I. V. Kinetics and Catalysis 1998, 39, 485; and Jiao, X. J.; Espenson, J. H. Inorg. Chem. 2000, 39, 1549.

TABLE 9 Results from semi-batch reactions performed as described above using 5-AMF feed.* Factor 3 Response Response Factor 1 Factor 2 Cobalt Factor 4 1 2 Temperature Pressure conc Br conc % yield of % yield of Run (° C.) (psig) (ppmw) (ppmw) FDCA FFCA 9a 180 130 2500 2500 44.6 0.25 9b 130 130 2500 2500 88.2 0.25 9c 155 130 2000 3000 67.6 0.026 9d 130 130 2000 3000 90.2 0.16 9e 155 130 2500 2500 64.52 0.35 9f 180 130 2000 3000 49.5 0.15 9g 105 130 2000 3000 64.8 1.8 9h 180 130 2000 3000 42.3 0.007 9i 180 130 2500 2500 40.9 0.06 9j 130 130 2000 3000 86.9 0.79 9k 130 130 2500 2500 88.5 0.71 *Cobalt to Manganese weight ratio = 21 for all experiments

As can be seen from FIG. 6, under the reaction conditions investigated, in this invention, the factor that has the most impact on the yield of FDCA is temperature. It is also important to note that the yield can increase with increasing cobalt and bromine concentrations.

It is important to note that the same yield and selectivity can be obtained with mixed 5-HMF and 5-AMF feed-stocks with varying ratios of the two components.

5-EMF Feed Study:

Oxidation of 5-EMF, which contains an oxidizable ether and aldehyde moieties, produced FDCA, FFCA, 5-(ethoxycarbonyl)furan-2-carboxylic acid (EFCA) and acetic acid, eq 9.

Experiments 10a-10k, Table 10, were conducted by varying temperature, and levels of cobalt and bromine concentrations to determine optimum conditions and catalyst compositions that produces very high yield of FDCA with minimum amount of carbon burn. Similar to the 5-AMF oxidation described above the weight ratio of cobalt to manganese was deliberately kept very high (i.e. 21) in all the reactions to avoid the inhibiting effect of excess manganese especially below 160° C.

TABLE 10 Results from semi-batch reactions performed as described above using 5-EMF feed.* Factor 3 Factor 1 Factor 2 Cobalt Factor 4 Response 1 Response 2 Response 3 Temperature Pressure conc Br conc % yield of % yield of % yield of Run (° C.) (psig) (ppmw) (ppmw) FDCA FFCA EFCA 10a 180 130 2500 2500 52.3 0.031 0.117 10b 130 130 2500 2500 88.8 0.02 0.225 10c 155 130 2000 3000 57.5 0.058 0.28 10d 130 130 2000 3000 87.97 0.09 0.43 10e 155 130 2500 2500 64.52 0.35 0.47 10f 180 130 2000 3000 49.5 0.15 0.23 10g 105 130 2000 3000 86 2.92 1.4 10h 180 130 2000 3000 50.9 0.096 0.24 10i 180 130 2500 2500 48.9 0.4 0.61 10j 130 130 2000 3000 87.5 0.4 1.22 10k 130 130 2500 2500 87.4 0.42 1.3 *Cobalt to Manganese weight ratio = 21 for all experiments

As can be seen from FIG. 7, under the reaction conditions investigated in this invention the factor that has the most impact on the yield of FDCA is temperature. It is important to note that the same yield and selectivity can be obtained with mixed 5-HMF and 5-EMF feed-stocks with varying ratios of the two components.

5-MF Feed Study:

Oxidation of 5-MF, which contains an oxidizable methyl and aldehydesmoieties, produced FDCA, and FFCA eq 10. Experiments 11a and 11b, Table 11, demonstrate that moderate yield of FDCA with high purity can be obtained using 5-MF as a feed stock.

TABLE 11 Results from semi-batch reactions performed as described above using 5-MF feed.* Factor 2 Factor 3 Factor 4 Response Response 2 Response 3 Factor 1 Pressure Cobalt Conc Br Conc 1 % yield % yield Temperature (psig) (ppmw) (ppmw) % of of Run (° C.) psi ppm ppm conversion FDCA FFCA 11a 130 130 2000 3000 100 61.3 0.082 11b 130 400 2500 2500 100 61.8 0.083 *Cobalt to Manganese weight ratio = 21.

It is very important to note that in a continuous process under the same conditions as described in this invention report (which was conducted as a batch process) with different feed stock even higher yields of crude FDCA is expected due to efficient mixing, relatively low concentrations of reactive intermediates, and other reasons familiar to those skilled in the art.

Claims not Limited to Disclosed Embodiments

The preferred forms of the invention described above are to be used as illustration only, and should not be used in a limiting sense to interpret the scope of the present invention. Modifications to the exemplary embodiments, set forth above, could be readily made by those skilled in the art without departing from the spirit of the present invention.

The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as it pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims. 

We claim:
 1. A process for producing a carboxylic acid composition, said process comprising: oxidizing in a primary oxidation zone at least one oxidizable compound in an oxidizable raw material stream comprising at least one selected from the group consisting of 5-HMF esters (5-R(CO)OCH₂-furfural where R=alkyl, cycloalkyl and aryl), and 5-HMF ethers (5-R′OCH₂-furfural, where R′=alkyl, cycloalkyl and aryl), in the presence of a solvent stream comprising acetic acid, an oxidizing gas comprising oxygen, and a catalyst system at a temperature of about 110° C. to about 160° C. to produce said carboxylic acid composition comprising furandicarboxylic acid at a yield of 80% or more; wherein sad primary oxidation zone comprises at least one oxidation reactor and wherein said catalyst system comprises cobalt in a range from about 500 ppm by weight to about 6000 ppm by weight with respect to the weight of the liquid in the primary oxidation zone, manganese in an amount ranging from about 2 ppm n by weight to about 600 ppm by weight with respect to the weight of the liquid in the primary oxidation zone and bromine in an amount ranging from about 300 ppm by weight to about 4500 ppm by weight with respect to the weight of the liquid in the primary oxidation zone wherein said carboxylic acid composition has a b* value less than
 15. 2. A process according to claim 1 wherein said oxidation reactor comprises a bubble column.
 3. A process according to claim 2 wherein said catalyst comprises cobalt in a range from about 700 ppm to about 4500 ppm by weight with respect to the weight of the liquid in the primary oxidation zone, manganese in an amount ranging from about 20 ppm by weight to about 400 ppm by weight with respect to the weight of the liquid in the primary oxidation zone and bromine in an amount ranging from about 700 ppm by weight to about 4000 ppm by weight with respect to the weight of the liquid in the primary oxidation zone.
 4. A process according to claim 1 wherein said catalyst comprises cobalt in a range from about 1000 ppm to about 4000 ppm with respect to the weight of the liquid in the primary oxidation zone, manganese in an amount ranging from about 20 ppm to about 200 ppm by weight with respect to the weight of the liquid in the primary oxidation zone and bromine in an amount ranging from about 1000 ppm to about 4000 ppm by weight with respect to the weight of the liquid in the primary oxidation zone.
 5. A process according to claim 1 wherein said carboxylic acid composition comprises at least one carboxylic acid selected from the group consisting of FDCA and FFCA.
 6. A process according to claim 1 wherein said carboxylic acid composition comprises FDCA.
 7. A process according to claim 1 wherein said oxidizing is conducted at a temperature from about 105° C. to about 180° C.
 8. A process according to claim 2 wherein said oxidizing is conducted at a temperature from about 110° C. to about 160° C.
 9. A process according to claim 1 wherein said oxidizing is conducted at a pressure from about 50 psig to about 1000 psig.
 10. A process according to claim 1 wherein said oxidizing is conducted at a pressure from about 50 psig to about 400 psig.
 11. A process according to claim 1 wherein said oxidizable raw material stream pH ranges from about −4.0 to about 1.0.
 12. A process according to claim 1 wherein said oxidizable raw material stream pH ranges from about −1.8 to about 1.0.
 13. A process according to claim 1 wherein said oxidizabie raw material stream pH ranges from about −1.5 to about 1.0. 